​Manchester United have had a €110m bid for Napoli defender Kalidou Koulibaly rejected by the Serie A side, with I Partenopei reiterating that the centre back is not for sale.

United have been enamoured with Koulibaly for some time, and are widely understood to have submitted a €100m bid for the Senegalese international last summer, which was also rejected.

Kalidou Koulibaly

And, according to reports in La Gazzetta dello Sport, as relayed by ​Football Italia, the Red Devils have gone back in for the Napoli man once more this summer, with the same result. 

It is understood that, just like his predecessor Jose Mourinho, Ole Gunnar Solskjaer sees Koulibaly as the best possible rearguard reinforcement the ​Red Devils could make this summer.

However, the Italian side's club president Aurelio de Laurentiis, having admitted to rejecting the €100m bid from an unnamed Premier League team understood to be United last summer, is once again having none of it. 

He considers the €110m figure (which roughly translates to £96.4m) far too low for his star centre half, and looks set to force Solskjaer and co to wait a further year until the summer of 2020, whereby the defender's release clause of €150m will become active. 

Koulibaly was recently named the ​Serie A Defensive Player of the Year for the 2018/19 season, after helping his side to 13 league clean sheets in 37 games. 

One man whose release clause United might have more immediate success with is Thomas Partey, with the Atletico Madrid midfielder, as per ​Football Ghana, apparently available for £43.5m this summer and the English club more than willing to pay for it.